RESERVOIR SIMULATION USING MBAL (A CASE STUDY OF RZD FIELD

ABSTRACT


Fluid flow in a petroleum reservoir is a very complex phenomena and it is impossible to develop

analytical  solutions  for  practical  issues  due  to  the  complex  behaviour  of  multiphase  flow.

Reservoir  simulation  study  the  behaviour  of  fluid  flow  and  provides  numerical  solutions  to

hydrodynamic  problems  of  fluids  in  the  petroleum  reservoir-well  systems  with  the  help  of  a

simulator. Reservoir simulation is used to predict the future performance of the reservoir so that

intelligent decision can be made to optimize the economic recovery of hydrocarbons from the

reservoir.  In  this  study  MBal  software  was  the  simulator  tool  used.  The  study  shows  the

application of MBal in predicting the future performance of the well. A work flow was applied for

this study and Data was gotten from RZD field and inputted to MBal, where result was gotten.

MBal software calculation estimated STOIP as 149.184MMSTB, predict volume of the water influx

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as 47268.8MMft, also show the effect of aquifer on the pressure of the reservoir and show that

water drive is the predominant drive mechanism responsible for production. Also history matching

and prediction run was done and it was predicted that the reservoir was to have a life span of 33

years with a recovery factor of 81.7%. This project show the importance of MBal in prediction of

future performance.  


 

 

 

 

 

 

 

 

 

 

  


 
RESERVOIR SIMULATION USING MBAL (A CASE STUDY OF RZD FIELD 1

 
                                    CHAPTER ONE


INTRODUCTION


1.0 Brief Overview

A  petroleum  reservoir  is  an  underground  porous  and  permeable  rock  medium  that  contains

naturally accumulation of producible hydrocarbon, which are confined by impermeable rock and

sometimes by water barriers. Fluid flow in such a porous medium is a very complex phenomena.

Generally,  analytical  solutions  to  mathematical  models  are  only  obtainable  after  making

simplifying assumptions in regard to the reservoir geometry, properties and boundary conditions.

However, such simplifications are often invalid for most fluid flow problems. In many cases, it is

impossible  to  develop  analytical  solutions  for  practical  issues  due  to  the complex  behaviors  of

multiphase  flow,  nonlinearity  of  the  governing  equations,  and  the  heterogeneity  and  irregular

shape of a reservoir system. As a result, these models must be solved with numerical methods such

as finite difference or finite element. Reservoir Simulation is an area of reservoir engineering in

which computer models are used to predict the flow of fluids (typically, oil, water, and gas) through

porous media (Okotie 2015). Reservoir simulation provides numerical solutions to hydrodynamic

problems  of  fluids  (oil,  gas  and  water)  in  petroleum  reservoir-well  systems  with  the  help  of  a

simulator.  Today,  it  has  become  a  standard  tool  in  petroleum  engineering  discipline  and  been

widely used for solving a variety of fluid flow problems involved in recovery of oil and gas from

the porous media of reservoirs.


1.1. Background of Study

Reservoir  Simulation  is  the  process  of  mimicking  or  inferring  the  behavior  of  fluid  flow  in  a

petroleum reservoir system through the use of either physical or mathematical models (chevron

2006). The process of reservoir simulation to predict the performance of a petroleum  reservoir

continues  throughout  the  life of the  field,  meaning  performance  prediction  is  updated  over the

producing  life  of  the  reservoir  as  more  data  becomes  available.  The  application  of  reservoir

simulation is to predict future performance of the reservoirs so that intelligent decisions can be

made to optimize the economic recovery of hydrocarbons from the reservoir. Reservoir simulation

can also be used to obtain insights into the dynamic behavior of a recovery process or mechanism.



 
RESERVOIR SIMULATION USING MBAL (A CASE STUDY OF RZD FIELD 2

 
Reservoir simulation make use of tools (SIMULATOR) to carry out these process. In this study,

MBal software will be the simulator tool to be used.


MBAL is a simulation tool made up of various tools designed to help the engineer to gain a better

understanding  of  reservoir behavior  and  perform  prediction  run.  The various  tools  available in

MBAL are (MBAL user manual, 2005); 


   Material Balance

   Reservoir Allocation

   Monte Carlo Volumetric

   Decline Curve Analysis,

   1-D Model (Buckley-Leverett) and 

   Multi-layer


The tool to be used in MBAL for this project is material balance.


1.1.1 Material Balance

Material balance equation is based on the application of the equation of conservation of mass to

petroleum reservoir for the purpose of making quantitative deduction.


                                                                

                                        IN                                                                 OUT


                                                   

                                                        IN – OUT = ACCUMULATION 


Fig 1.1: Showing the diagram for conservation of mass


  IN – Amount of fluids present in the reservoir initially (vol)


  OUT – Amount of fluids produced (vol)


  ACCUMULATION – Amount of fluids remaining in the reservoir finally (vol)                                            


 It was developed by Schilthius in 1936, it covers area that contributes to the pressure production

history.  Material  balance uses  actual  reservoir  performance  data  and  therefore  is  generally


 
RESERVOIR SIMULATION USING MBAL (A CASE STUDY OF RZD FIELD 3

 
accepted  as  the  most  accurate  procedure  for  estimating  original  oil  and  gas  in  place.  It  is  the

reservoir engineer’s basic tool for interpreting and predicting reservoir performance.


The material balance uses a model that is existing as an imagination of the reservoir to actually tell

or forecast the behaviour of the reservoir established on the effects of production of fluid from the

oil pool and injection of gas and water. The material balance equation is considered to be a tank

model which implies that there is no time parameter in the area produced. The ways at which the

wells are drilled into the reservoir are positioned and oriented alongside with the dynamic effects

of fluid which are not considered, hence the heterogeneous nature of the reservoir do not reflect,

but it is still being used by Reservoir Engineers as a tool for interpreting and predicting reservoir

performance. In the cause of this study, to illustrate the method, only sections specifically dealing

with the material balance principles are included. Additional geologic information and basic data

are reported to better acquire an understanding of the cases and thus to better follow the reasoning

that suggested the successful application of the straight-line method of solving the MBE.


Table 1.1 Data required for MBE


Data  Source

PVT Data  From PVT reports, correlations

Production data  Well and reservoir records

Ratio of gas cap volume to oil volume From wireline log, reservoir modeling

(M)

Oil and gas in place   From volumetric estimate and geological model

Connate water saturation  From petrophysics (core and log)

Water compressibility  From correlation or measured

Pore compressibility  From correlation or measured 

Reservoir pressures  From pressure survey

Water influx  Calculation or history

 


The accuracy of material balance is based on the consistency of results when applied at successive

intervals and agreement of the Material balance equation (MBE) result with result gotten from

volumetric technique.